Groundcover on a steep hill

I have a very steep hillside facing east, heavy clay soil, lots of sun in summer, lots of rain all winter and spring (Pacific Northwest). Can you suggest a good groundcover, other than ivy, that might work well there? It is difficult to work on, so the groundcover needs to be thick enough to keep weeds and grass down. I'd love an evergreen that blooms sometime during the year.

One of my favorite ground covers is Dwarf plumbago (Ceratostigma plumbaginoides). It is not picky about soil, sun or water conditions and will thrive on a hillside. It has glossy green leaves that turn bronzey-red in fall. In late summer, it blooms true-blue, although I have seen flowers in Zone 7 as early as July. The problem is, it's semi-evergreen; the leaves do disappear in winter. I leave the red stems with their burr-like seedheads on throughout the year. You could interplant with taller Artemisia x 'Powis Castle' for year-round greenery. This Artemisia thrives in clay soil.